Anti-static additives for hydrocarbon oils



United States Patent Ofilice 3,240,009 Patented Mar. 15, 1966 3,240,009 ANTI-STATIC ADDITIVES FOR HYDRO- CARBON OILS Harold C. Walters, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware N Drawing. Filed Mar. 23, 1962, Ser. No. 182,102 Claims. (Cl. 60-35.4)

This invention relates to hydrocarbon oils having improved electrical properties. In a specific aspect, this invention relates to the minimizing of tribo-electrical discharges by increasing the electrical conductivity of hydrocarbons oils.

It has been observed that a number of accidents involving the ignition of hydrocarbon fuels could be explained on the basis of tribo-electrical discharges caused by movement of the fuel or movement of other objectsor fluids through the fuel. It has been postulated that ionizable particles in the fuel are attracted to solid surfaces such as the sides of fuel tanks or pipelines. Thus, movement of the fuel sweeps away some of the particles of opposite polarity tending to create an electrical charge on the fuel. If this charge is permitted to accumulate, the danger of a sudden electrical discharge exists. If such should occur in the presence of a combustible mixture of fuel and air, such as might exist in the vapor space of a storage tank during loading, ignition and explosion can be the result. It is to be noted that hydrocarbons in the jet fuel range are particularly susceptible to accidental explosion as they form explosive mixtures over a wide range of air concentrations. It has been observed that hydrocarbon fuels which are void of ionizable contaminants such as residues, degradation or oxidation products, do not readily become charged.

It has further been observed that while traces of ionizable material cause static charges to be developed, increasing the concentration of polar material increases the conductivity of the fuel to the point that the charge may be safely conducted away. Thus, by adding an ionizable material to the hydrocarbon fuel, the ability of the fuel to dissipate static charges surpasses its ability to develop them. The hydrocarbon fuel to which a polar material has been added exhibits a relatively high electrical conductivity and is less likely to be ignited by a sudden electrical discharge. It has been observed that a hydrocarbon fuel with an intermediate conductivity of 1 to 1 10 ohm -cm.- is capable of becoming dangerously charged. Therefore, it is desirable to provide an antistatic additive to the hydrocarbon fuel which will increase the conductivity of the fuel to l l0 ohmcm. or greater.

Ionizable materials, in general, have little or no solubility in hydrocarbon oils. The ionizable material selected as the additive to be employed must be soluble in the hydrocarbon oil and compatible with the hydrocarbon oil with regard to operational characteristics. This is to say, that the additive must not detract from the utility of the hydrocarbon oil.

Accordingly, an object of my invention is to improve the electrical properties of hydrocarbon oils.

Another object of my invention is to increase the electrical conductivity of hydrocarbon oils.

Another object of my invention is to improve the operation of jet aircraft.

Other objects, features, and advantages of my invention will be readily apparent to those skilled in the art from the following description and the appended claims.

I have discovered that the electrical conductivity of hydrocarbon oils is substantially improved by the addition of a derivative of pyrrole to said hydrocarbon oils.

The process of this invention is applicable to hydro carbon oils having a Reid vapor pressure of less than 5.0 and boiling below 750 F., employing vapor pressure (D323) and distillation (D86) tests outlined in ASTM Standards on petroleum products and lubricants prepared by ASTM Committee D2, published in 1960 by the American Society for Testing Materials, 1916 Race Street, Philadelphia 3, Pennsylvania. The type of hydrocarbon oils to which this invention is applicable include petroleum dist-illates such as kerosenes, diesel fuels and heating oils. The invention is particularly applicable to jet fuels, such as for example, conforming to military specification Mil- J-S 624E and designated as JP-4 and JP-S fuels.

An additive sufiiciently soluble in hydrocarbon oils and capable of increasing the electrical conductivity in the hydrocarbon oil is selected from hemin and a chlorophyll group compound containing 4 pyrrole nuclei. The chlorophyll group compounds consist of chlorophyll a, chlorophyll b, chlorophyllide a, chlorophyllide b, methylchlorophyllide a, methylchlorophylide b, ethychlorophyllide a, ethylchlorophyllide b, pheophytin a, pheophytin b, pheophorbide a, pheophorbide b, methylpheophorbide a,

methylpheophorbide b, ethylpheophorbide a, ethylpheo-- phorbide b, phytochlorine e phytorhodine g potassium chlorophyllin a, and potassium chlorophyllin b. Hemin and/ or chlorophyll group compounds can be added to the hydrocarbon oil over a broad concentration range. The concentration of the additive in the hydrocarbon oil can range from about 0.05 to about 1000 ppm. by Weight, preferably 10-200. The chlorophyll group compounds of this invention may be purified materials resulting from the extraction, processing, and chemical treating of naturally occurring materials which contain them. On the other hand, mixtures of two or more members of this group may be used including such commercially available mixtures containing chlorophyll a, chlorophyll b, and minor amounts of colored and colorless plant constituents such as carotenoids, fats, oils, waxes and resins.

The additive can be added to the hydrocarbon oil in any conventional way which assures uniform solution and distribution. The additive can be dissolved directly into the hydrocarbon oil with agitation or it can first be dispersed in an appropriate solvent such as benzene or toluene to form a concentrate which is then added to the hydrocarbon oil. The additive can be utilized in jet fuels containing an anti-icing additive such as a blend of a saturated acylic polyhydric alcohol and a glycol ether. Specifically the above anti-icing additive comprises a blend of a saturated acyclic polyhydroxy alcohol containing from 3 to 5 carbon atoms; from 2 to 5 OH groups, each attached to a different carbon atom and wherein the ratio of OH groups to carbon atoms is in the range of 0.66:1 to 1:1; and a glycol ether having the formula The following examples are presented as illustrative of U the effectiveness of the inventive process. It is not intended, however, that the invention should be limit-ed thereto.

Example I A JP-4 jet fuel having an API gravity of 56.4, a Reid vapor pressure of 2.9, and having a distillation range as follows:

and otherwise conforming to the military specification MilJ-5624E, was treated with three different concentrations of chlorophyll (Fisher Scientific Company Cat. No. C307). The resulting mixtures were tested for electrical conductivity on an apparatus such as that described in Theoretical and Experimental Observations of Static Electricity in Petroleum P oducts, by Rogers, McDermot, and Munday, presented at the 37th Annual Meeting of API in Chicago on November 12, 1957.

The conductivity of the untreated JP-4 fuel was also measured for comparison with the I P4 plus additive runs. The results are illustrated in Table I.

TABLE I Specific Conductivity (hmem.-

Hydrocarbon Fuel JP-4 plus 100 p.p.m. chlorophyll Example II As illustrative of the compatibility of the additive with turbine fuels, a sample of turbine fuel kerosene (JP5) containing 60 p.p.m. chlorophyll was subjected to a CPR Fuel Coker Test. The turbine fuel employed had a gravity of 45.0 at 60 F. and had a distillation range (D-86) as follows:

Percent distilled: Distillation temp., F.

IBP 321 366 The test procedure employed was the Tentative Standard Method 3464T (June 1, 1957), for the thermal stability of gas turbine fuels (part of Federal Test Method Standard No. 791 and described in the Coordinating Research Council, Inc., Manual No. 3). The results of this test are illustrated in Table II.

TABLE II Test Temp, F. Filter Max. Tube Merit Min. to 25 AP to Rating Rating Hg AP 300 min. Preheater Filter The above data conclusively indicate that the additive is compatible with the turbine fuel with regard to thermal stability.

Example III In order to demonstrate the compatibility of the additive and an anti-icing additive in a hydrocarbon fuel, the combination of the two additives was tested in a sample of Soltrol 130. The Soltrol 130 (a virtually 100% isoparafiinic hydrocarbon) employed in the following runs exhibited an API gravity of 55.7 at 60 F. and had the following distillation range (ASTM D86):

Percent distilled: Distillation temp, F. IBP 347 5 352 10 354 20 356 30 358 40 360 362 364 365 373 381 389 BR 409 Rec., 98.1 Res, 1.4

The anti-icing additive employed was comprised of 90 parts by volume of methyl cellosolve and 10 parts by volume of glycerine.

The results are illustrated in Table III. The chlorophyll was added to Soltrol as a 25 volume percent solution in toluene.

TABLE III Specific Test No. Fuel Conductivity (ohmcrnr 1 Soltrol130 0.89 l0- Soltrol 130 plus 0.1 vol. percent Anti- 0.70 10- Icing Additive. 2 Soltrol 130 0.76 10' Soltrol 130 plus 40 p.p.m. chlorophyll 401 1o- Soltrol 130 plus 40 p.p.m. chlorophyll 174 10- plus 0.2 vol. percent Anti-Icing Additive.

The above data conclusively show the compatibility of chlorophyll and the anti-icing additive with regard to electrical conductivity. The addition of the anti-icing additive to a hydrocarbon fuel containing chlorophyll does not appreciably change the electrical conductivity of the hydrocarbon fuel within reproducible test results.

As will be evident to those skilled in the art, various modifications of this invention can be made, or followed, in the light of the foregoing disclosure and discussion Without departing from the spirit or scope thereof.

I claim:

1. In the method of operating a jet aircraft which comprises passing a hydrocarbon fuel having a Reid vapor pressure less than 5.0 and boiling below 750 F. to the combustion zone of said jet aircraft, the step of increasing the electrical conductivity of said hydrocarbon fuel to at least 1 1O ohm cm. by the addition thereto of an additive selected from the group consisting of hemin and chlorophyll group compounds containing 4 pyrrole nuclei.

2. The method of claim 1 wherein the concentration of said additive is in the range from about 0.05 to about 1000 parts per million by weight.

3. The method of claim 2 wherein said additive is chlorophyll.

4. In the method of operating a jet aircraft which comprises passing to the combustion zone of said jet aircraft a hydrocarbon fuel having a Reid vapor pressure less than 5.0 and boiling below 750 F., the step of increasing the electrical conductivity of said hydrocarbon fuel to at least 1 l0 ohm'" cm. by the addition thereto of from about 0.05 to about 1000 parts per million by weight of an additive selected from the group consisting of hemin and chlorophyll group compounds containing 4 pyrrole nuclei, said hydrocarbon fuel containing a concentration in the range of about 0.1-0.2 weight percent of an antiicing additive comprising a blend of a saturated acyclic polyhydric alcohol and a glycol ether.

5. The method of claim 4 wherein said anti-icing additive is a blend of methyl ethylene glycol monoethyl ether and glycerine.

. References Cited by the Examiner UNITED STATES PATENTS DANIEL E. WYMAN, Primary Examiner. 

1. IN THE METHOD OF OPERATING A JET AIRCRAFT WHICH COMPRISES PASSING A HYDROCARBON FUEL HAVINGA REID VAPOR PRESSURE LESS THANT 5.0 AND BOILING BELOW 750*F. TO THE COMBUSTION ZONE OF SAID JET AIRCRAFT, THE STEP OF INCREASING THE ELECTICAL CONDUCTIVITY OF SAID HYDROCARBON FUEL TO AT LEAST 1X10**-11OHM**-1CM.**-1 BY THE ADDITION THERETO OF AN ADDITIVE SELECTED FROM THE GROUP CONSISTING OF HEMIN AND CHLOROPHYLL GROUP COMPOUNDS CONTAINING 4 PYRROLE NUCLEI. 